1.0 Field of the Disclosure
The present disclosure is directed to a cap for a container closure and, in particular, to a cap with a sealing disc.
2.0 Related Art
On the closure of a container it is frequently desirable, or even necessary, to provide the container mouth with a disc-shaped closure which seals off the contents, for example, liquids or else substances such as foodstuffs.
There are several reasons why the sealing off is required. On the one hand, the contents are to be protected against outside influences, for example, against water vapor or oxygen. On the other they are also to remain aroma-tight. There is a further reason in the case of aggressive contents, for which leakage protection must be optimized. Finally, an originality protection for the trade also may be provided by such a sealing off, because a user is able to recognize immediately whether someone has already handled the container contents beforehand.
In addition, the container closure is then also sealed with a screw cap or a similar element, which ensures a mechanical and stable sealing outside the film. On initial use the user destroys the film in order to obtain access to the contents of the container. The user may then close the container afterwards (unless he has already removed the entire contents) with the screw closure, which may provide a temporary seal for the opened contents for a suitably short period of time.
The film that seals the container contents is frequently applied by induction sealing. A complete sealing disc is put on for this purpose, having a bottom layer that forms the sealing layer. Above the sealing layer lies a second layer, generally aluminum, which serves for the generation and transmission of heat during the induction process and optionally forms an additional mechanical protection. The second layer is firmly connected to the first layer and in particular favorably for the transmission of heat. Above the second, aluminum layer are further components of the sealing disc, which remain in the cap after opening the screw or other rotating closure.
The removal of the film is irksome for the user in certain circumstances, which may require a tool, for example, a knife or a pair of scissors. Use of a tool leads to the risk that parts of the film will thereby fall into the container contents. In addition, a suitable tool is not always at hand. Screw closures already exist with an outside so formed that when used the other way round they permit a partial cutting or tearing of the film here. This makes the screw cap more expensive, and it is also necessary to give the user suitable instructions on the method, so that he may carry out the opening correctly.
It has also already been proposed as an alternative, for example in EP 0 697 345 A2, that the sealing disc, or at least the film composite, be provided at its edge with suitable projections or tabs, which the user may grasp, thus allowing the user, supported in this way, to easily remove the sealed-on film. The extremely practical construction may not be used in every case, however, because the projecting tabs must, after the positioning of the screw cap, be able to be arranged between the screw thread and the outside of the container opening, a fact which may lead to geometrical difficulties. It is also problematical if, for example, the upper parts of the sealing disc must not exhibit any lugs, because this prevents their retention in the screw cap part. Two separate punching operations would then have to be provided for the film composite and the upper parts of the sealing disc, which leads to further costs.
It has therefore been proposed in EP 0 395 660 B1 and EP 0 534 949 B1 that the sealed-on film composite be constructed of two layers that are bonded to one another over roughly half of their area, while the other half remains free. This results in easy detachment of the half of the upper layer that is not bonded, whereas the other area remains connected during the detachment. If such a two-layered, partially bonded film composite is used on the container, the user simply has to grasp the admittedly flatly positioned but easily detachable half of the upper layer, and is then able to remove the whole of the film composite by exerting a suitable force.
This rather striking idea nevertheless has some drawbacks. A mass market product is naturally involved, in which cost considerations play a very great role. A process must therefore be found in which two layers may be connected to one another in such a way that they are only partially bonded. This can be brought about by a relatively laborious strip-wise lamination.
A further drawback is due to the partially open upper layer, which causes problems during the filling and closing of the containers. If the screw closure is applied with rotation, the latter has a tendency to attack the film by friction. As the upper layer is supported loosely in part, it is on some occasions also pulled slightly here, which may lead immediately to uncontrolled creasing and also to buckling and to destruction. In the container filling industry, however, even minimal wastage rates are extremely undesirable because, as a rule, the whole container then has to be rejected or may lead to complaints.
The object of the present disclosure is therefore a sealing disc and a sealing film for a container closure which also leads to an easy opening of the film for the user, but at the same time is also convenient and reliable in manufacture and does not require additional punching operations.